In recent years, semiconductor devices have been developed which are capable of supplying (also referred to as feeding) power (also referred to as a power supply voltage) through wireless communication, and further capable of transmitting and receiving data (also referred to as data communication) through wireless communication. For example, if a feeding function through wireless communication can be added to a portable information medium (e.g., a cellular phone) which is an example of the semiconductor devices, the portable information medium does not need to be connected to an external power feeding portion and can be fed more easily, for example, in any environment.
An individual identification technology utilizing an RFID (radio frequency identification) tag is known as an example of semiconductor devices capable of data transmission, data reception, data storing, data erasing and the like through wireless communication. The RFID tag is also referred to as an RF tag, a wireless tag, an electronic tag, or a wireless chip. The RFID tag is also referred to as an IC tag, an IC chip, or an IC card because it includes a functional circuit such as an integrated circuit (IC) for executing authentication or other processing. Data communication with the semiconductor device is performed by using a wireless communication device (such as a reader/writer, which is capable of transmitting and receiving a data signal through wireless communication). The individual identification technology using the semiconductor device is used for the production, management, or the like of an individual object and has been expected to be applied to personal authentication.
In general, the semiconductor device does not include in itself a power generating means and is fed through wireless communication; thus, the semiconductor device can be fed even at a distance from a feeding means. The distance over which wireless communication is possible is also referred to as a communication distance. In a semiconductor device externally supplied with power, the feeding efficiency generally tends to decrease as the communication distance increases. Therefore, semiconductor devices to which a desired amount of power can be supplied even at a long communication distance have been researched and developed (see Patent Document 1).